The present invention relates to a heat exchanger, particularly for use as a rack evaporator in refrigerators or freezers, and to a process for manufacturing it.
As is known, refrigerators are generally constituted by a box-like structure having an internal chamber which is kept at a controlled temperature by means of a refrigeration circuit. In order to achieve higher efficiency of the refrigeration circuit and keep the temperature inside refrigerators as uniform as possible, rack evaporators are generally used, arranging an evaporator coil in each shelf of the refrigerator and mutually connecting the evaporator coils of the various shelves that form, as a whole, the evaporator of the circuit.
More particularly, each shelf comprises a coil constituted by a tubular body extending along a path in which bends alternate with straight and substantially mutually co-planar portions, and by a supporting structure, which can be constituted by a plurality of parallel rods welded on at least one of the two faces of the coil or by a plate-like element which is seamed, welded or glued or otherwise rigidly connected to one side of the coil, has the purpose of forming a supporting surface suitable to support the products to be arranged on the shelves, and at the same time increases the heat-exchange surface of the coil.
Usually, the evaporator constituted by the coils forming the various shelves of the refrigerator, as well as the portions of the evaporator that mutually connect the various coils, are formed by shaping a plurality of separate tubular bodies (coils), subsequently assembled together with the rods or with the plate, thus forming the shelf which is in turn assembled together with other shelves by welding, forming the evaporator as a whole. The evaporator, in its final configuration, is thus constituted by a plurality of coils extending along mutually parallel and superimposed planes and mutually connected by tubular portions extending vertically between the various planes. Since each shelf has a substantially rectangular shape, the evaporator substantially has, as a whole, the shape of a parallelepiped in which the tubular portions connecting the various shelves are located generally at one or more of the edges of such a parallelepiped.
These known rack evaporators have some drawbacks, particularly as regards the bulk, due to the stacked arrangement of the various shelves and to the presence of the tubular portions connecting the various shelves.
A rack evaporator of the type described above in fact requires very large spaces which can entail problems during packaging, shipping and possible treatments to which the evaporator must be subjected. Furthermore, in the case of evaporators constituted by a plurality of separate shelves subsequently joined in the circuit by welding, a certain defectiveness can be noted due to leakage of the refrigerating gas from defective braze welds. Alternatively, the evaporator, with its shelves and various tube portions mutually connecting them, can be formed by means of the shaping of a single tubular body, followed by the welding of rods or by the seaming of the plate for each shelf and by the final shaping of the evaporator with parallel shelves.
In order to solve the drawback of bulk during packaging, shipping or treatment, in some rack evaporators the tubular portions that mutually connect the coils of the various shelves are arranged along a single edge of the parallelepipedal space occupied by the evaporator, and during packaging and shipping the shelves of other similar rack evaporators are inserted between two superimposed contiguous shelves of a same evaporator. This solution only partially solves the drawbacks linked to the packaging and shipping of rack evaporators, since the coupling of a plurality of rack evaporators significantly complicates packaging operations and makes it difficult to disengage the evaporators when they are used.
Furthermore, this contrivance to reduce the overall space required by rack evaporators cannot be adopted to reduce the individual bulk of each rack evaporator during possible treatments.
Furthermore, in known rack evaporators difficulties arise when bending the tubular body that constitutes the evaporator, particularly as regards the bending to which the portion connecting the coils between the various shelves must be subjected in order to always arrange this connecting portion at a single edge of the parallelepipedal space occupied by the evaporator.